WO2014082477A1

WO2014082477A1 - Protection method for data information about electronic device and protection circuit therefor

Info

Publication number: WO2014082477A1
Application number: PCT/CN2013/083258
Authority: WO
Inventors: 黄善兵; 翟建光; 吴红远
Original assignee: 深圳市新国都技术股份有限公司
Priority date: 2012-11-29
Filing date: 2013-09-11
Publication date: 2014-06-05
Also published as: US20150301919A1; CN103400078B; EP2919210A4; EP2919210B1; CN103400078A; US9772922B2; EP2919210A1; ES2678171T3; CN103035077A

Abstract

A method for protecting data information about an electronic device, comprising the following steps: 1) performing power-on detection on an electronic device of which production and installation are completed, detecting the stray capacitance of a signal line thereof, and recording same as a standard value of the signal line; 2)during a power-on operation, monitoring the stray capacitance of the signal line; 3)comparing the monitored capacitance value with the standard value, and entering step 4) when exceeding the set threshold value, otherwise entering step 2); and 4) erasing significant data in the electronic device. The method uses the manner of monitoring the stray capacitance to monitor the contact of outside foreign matter with the signal line, guarantees the security of data in the electronic device, and has the characteristics that the implementation process is simple and easy, safe and reliable, and the cost is low.

Description

Data information protection method for electronic device and protection circuit thereof

Technical field

The invention relates to a method for protecting data information and a protection circuit thereof, and more particularly to a data information protection method for an electronic device and a protection circuit thereof.

Background technique

The POS machine is a sales terminal with a non-cash settlement function. The card reader reads the cardholder magnetic stripe information on the bank card, and the cardholder inputs the personal identification information (ie, the password) to complete the online transaction. Used in supermarkets, chain stores, hypermarkets, restaurants and other places. Because of the online consumption of bank cards, there are high requirements for their security performance, and it is necessary to ensure that important data in the POS machine is not stolen.

At present, POS machines meet the data security standards. The methods used are mainly to surround important data lines or sensitive components with safety signal lines to prevent illegal personnel from detecting these important data lines and components. If the CPU detects the safety signal lines. As the level changes, the CPU erases all protected data.

Safety signal lines protect important data lines and sensitive devices mainly by winding technology, protective contact technology and zebra strip technology. The winding technology usually lays the safety signal line on the PCB board through certain principles and methods, and combines some PCB small boards, brackets, protective frames, etc. with windings to make the CPU and IC card chips in the safety signal line. In the encirclement, any attempt to use the probe, drill, move, etc. CPU will erase all protected data, but the design of the winding technology is more complicated and costly, and needs to be surrounded by CPU, IC card chip, etc. Line, development design cycle is relatively long.

The principle of the protective contact technology is a switch, which places the conductive adhesive on the contact and applies a certain pressure to achieve the closing of the switch. The zebra strip is also similar to a switch when the conductive interlayer in the middle of the zebra strip is subjected to a certain direction. The pressure on the upper part shows a certain continuity. The protective contacts and zebra strips are mainly used for tampering. When someone tries to open the POS case and separate the main board and the cover, the CPU will erase the protected data, but this The technical cost is relatively high.

In addition to POS machines, as well as ATM machines and various types of intelligent terminals, they need to be used by the public in an unattended situation, and there is a possibility of stealing important signals.

Therefore, it is necessary to develop an information data protection method and a protection circuit thereof which are low in cost and easy to maintain.

Summary of the invention

The object of the present invention is to overcome the deficiencies of the prior art and to provide a data information protection method for an electronic device.

It is a further object of the present invention to provide a data information protection circuit for an electronic device.

To achieve the above object, the present invention adopts the following technical solutions:

A method for protecting data information of an electronic device, the method comprising the following steps:

1) Perform power-on detection on the electronic equipment that has been completed for production and installation, and detect the stray capacitance of the signal line, and record it as the standard value of the signal line;

2) Monitor the stray capacitance of the signal line when powering up;

3) comparing the monitored capacitance value with the standard value, when the set threshold value is exceeded, proceed to step 4), otherwise, proceed to step 2);

4) Wipe important data in the electronic device.

The further technical solution is as follows: the signal lines are multiple, and when the power is detected, the standard values of the stray capacitances of the signal lines are recorded one by one; when the power is on, the stray capacitance of each signal line is sequentially monitored or randomly monitored. And compare it with its corresponding standard value.

The further technical solution is: the stray capacitance of the signal line adopts a direct monitoring method, and the direct monitoring method is to charge and discharge the stray capacitance of the signal line, monitor the voltage of the stray capacitance, and charge and discharge time, and then use the capacitor. The charge and discharge formula is used to determine the capacitance of the stray capacitance.

The further technical solution is that the stray capacitance of the signal line adopts an indirect monitoring method, and the indirect monitoring method is to calculate the oscillating frequency of the RC oscillating circuit or the LC oscillating circuit connected with the stray capacitance, and calculate the impurity by the formula of the oscillating frequency. The capacitance value of the bulk capacitor.

A further technical solution is that a selection circuit is disposed between each of the signal lines and the RC oscillating circuit or the LC oscillating circuit, and the connection of each signal line to the RC oscillating circuit or the LC oscillating circuit is turned on one by one by the selecting circuit.

A data information protection circuit for an electronic device, the electronic device is provided with a processor and an electronic device connected to the processor through a signal line, and includes a capacitance detecting module electrically connected to the signal line, wherein the capacitance detecting module is provided The detecting end is connected to the signal line, and the pulse detecting end of the capacitance detecting module is connected to the processor; when the electronic device is first powered on, the stray capacitance on the signal line and the pulse signal formed by the capacitance detecting module are transmitted to the processor. The processor records the frequency of the pulse signal as a standard frequency; during use, the processor compares the received real-time frequency with the standard frequency. When the difference between the real-time frequency and the standard frequency exceeds the set value, the processor determines that there is The foreign matter contacts the signal line, the stray capacitance on the signal line changes, and the pulse signal formed by the combination with the capacitance detecting module also changes, and the processor erases important data in the electronic device; the signal line is the electronic device and processing Connecting wires between the devices.

A further technical solution is: the capacitance detecting module is an RC oscillating circuit including an inverter; the signal lines are a plurality of; the multiplexer is disposed between the plurality of signal lines and the capacitance detecting module; .

The further technical solution is that the multiplexer is an 8-channel analog multiplexer, and has eight input terminals connected to the signal line and one output connected to the capacitance detecting module, and three processors. The connected control input terminal, the 8-channel analog multiplexer determines that one of the input terminals is connected to the output terminal according to the combined signals of the three control inputs; when the power is first turned on, the processor inputs 8 combined signals one by one to the 8-channel analog a multiplexer, and recording a pulse frequency generated by the signal line corresponding to each combined signal and the capacitance detecting module as a standard frequency corresponding to the combined signal; during use, the processor randomly or separately sends a combined signal, The received real-time frequency is compared with a standard frequency corresponding to the combined signal. When the difference between the real-time frequency and the standard frequency corresponding to the combined signal exceeds a set value, the processor determines that a foreign object contacts the combined signal. The signal line, the stray capacitance on the signal line changes, and the pulse signal formed by the combination with the capacitance detecting module is also generated. a change, a processor outputting an alarm signal and/or a signal for protecting important data; the electronic device is a POS machine, an ATM machine, or a cash register; the electronic device includes a button, a display screen, and an IC card reader/writer And magnetic card readers.

A data information protection circuit for an electronic device, the electronic device is provided with a processor and an electronic device connected to the processor through a signal line, and includes a capacitance detecting module electrically connected to the signal line, wherein the capacitance detecting module is provided The detecting end is connected to the signal line, the control end and the signal output end of the capacitance detecting module are connected to the processor; the capacitance detecting module is a capacitance detecting chip; when the electronic device is powered on for the first time, the capacitance detecting module detects the spur on the signal line. The capacitor is transmitted to the processor, and the processor records the capacitance value as a standard capacitance value; during use, the processor receives the capacitance value detected by the capacitance detecting module in real time and compares it with the standard capacitance value, when the real-time capacitance value and the standard When the difference between the capacitance values exceeds the set threshold, the processor determines that there is a foreign matter contacting the signal line, and the processor erases the important data in the electronic device.

A data information protection circuit for an electronic device, wherein the electronic device is a POS machine, and the data information protection circuit comprises:

The multiplex selection module is a multiplex selection chip, and the multiplex selection chip is 74HC4051, which has 8 external signal input terminals (A0 to A7) and 3 digital selection terminals (S0). To S2) and one signal output (A);

a capacitance detecting module (20), the capacitance detecting module (20) comprising a first inverter (U418A), a second inverter (U418B), and a third inverter (U418C), the first inverter (U418A) The input terminal (1) is connected to the output terminal (A) of the multiplex selection module (90) through the first capacitor (C35), and the output terminal (2) of the first inverter (U418A) and the second inverter The input terminal (3) of (U418B) is connected, the output terminal (4) of the second inverter (U418B) is connected to the input terminal (5) of the third inverter (U418C), and the first inverter (U418A) A first resistor (R1) is connected between the input terminal (1) and the output terminal (2), and an input terminal (1) of the first inverter (U418A) and an output terminal of the second inverter (U418B) ( 4) is connected between the second resistor (R2) and the second capacitor (C37) connected in series, and the connection point (8) of the two passes through the output of the third resistor (R3) and the third inverter (U418C) The terminal (6) is connected, and the input terminal (5) and the output terminal (6) of the third inverter (U418C) are connected to the output through the fourth resistor (R4) and the fifth resistor (R5), respectively. (Key-LED); a first inverter (U418A) of the power supply input (the VCC 33) connected in parallel through a third capacitance (C207) and a fourth capacitance (C135) to ground.

The beneficial effects of the present invention compared to the prior art are:

The protection method of the invention adopts a method for real-time monitoring of the signal line, and collects the change of the stray capacitance value on the signal line in real time, and when the change value exceeds the set threshold value, it is determined that the external conductor foreign object detects the signal line, In turn, the important data in the electronic device is erased, and the data in the electronic device is ensured. The method has the characteristics of simple implementation, safe and reliable, low cost, and can be applied to data security protection of various electronic devices in the field of informationization, such as electronic devices for electronic transactions and storage devices for important data.

The protection circuit of the invention adopts an indirect monitoring mode, and an oscillating circuit composed of an inverter and a resistor capacitor is connected to the detected wire, so that the variation of the stray capacitance on the detected wire causes a change in the oscillation frequency, and when there is a foreign matter contact, When the wire is detected, the processor detects a change in the oscillation frequency, thereby determining that there is foreign matter contact, and the processor inputs an alarm signal or an associated processing signal. The protection circuit is not only safe and reliable, but also has a short development cycle, low production cost, simple circuit structure, easy production and processing, and can be applied to different electronic devices; for example, POS machines, ATM machines, and the like. Since the important data information of the electronic device is detected from the outside, and some of the data wires may be intercepted, the present invention adopts a multiplexer, so that a plurality of detected wires share a capacitance detecting module, thereby saving cost and optimizing the circuit structure. . At the same time, the combined control signal of the processor is used to select one of the analog channels to be turned on, so that the unscrupulous person can only record the frequency signal of a detected wire before the removal of the capacitance detecting module, and the frequency signal is replaced. After that, it is difficult to match the combined control signals of the processor, and it is impossible to replace the frequency signals of other detected wires, thereby increasing the difficulty of stealing the electronic device; and greatly improving the security performance of the electronic device.

The protection circuit of the present invention can also use a capacitance detecting chip having a plurality of detecting ports to directly monitor the stray capacitances on the respective signal lines to determine whether the respective signal lines are contacted by the foreign matter of the conductor. The structure adopts the integrated chip method, and can monitor or randomly monitor the change of the stray capacitance of the signal lines of each detecting end in real time, and has the characteristics of simple circuit structure, low cost, easy production and easy maintenance, and is not easy to be cracked.

The technology of the present invention can be applied to POS products, and can also be used for electronic trading equipment such as ATM, and can also be used for storage of important data, such as a database of security management departments.

The invention is further described below in conjunction with the drawings and specific embodiments.

DRAWINGS

1 is a flowchart of a specific embodiment of a data information protection method for an electronic device according to the present invention;

2 is a block diagram (indirect monitoring mode) of a specific embodiment 1 of a data information protection circuit of an electronic device according to the present invention;

3 is a circuit schematic diagram 1 (a multiplexer part) of a second embodiment of a data information protection circuit of an electronic device according to the present invention;

4 is a circuit schematic diagram 2 (capacitance detection module portion) of a second embodiment of a data information protection circuit of an electronic device according to the present invention;

5 is a pulse waveform diagram of an input end and an output end of a capacitance detecting module according to a second embodiment of a data information protection circuit of an electronic device according to the present invention;

FIG. 6 is a schematic circuit diagram of a third embodiment of a data information protection circuit of an electronic device according to the present invention (chip part, direct monitoring mode).

DRAWINGS

10 POS machine 20 processor

30 electronics 40 tested wires

50 Capacitance Detection Module 51 Detection Terminal

52 pulse output 60 multiplexer

61 input 62 output

63 control input

detailed description

In order to more fully understand the technical content of the present invention, the technical solutions of the present invention are further described and illustrated in conjunction with the specific embodiments, but are not limited thereto.

As shown in FIG. 1 , a data information protection method for an electronic device according to the present invention includes the following steps:

1) Perform power-on detection on the electronic equipment that has been completed for production and installation, and detect the stray capacitance of the signal line, and record it as the standard value of the signal line; this process is usually implemented when the product is tested at the factory.

2) Monitor the stray capacitance of the signal line when the power is on; the process is synchronized with the startup process of the electronic device, and the monitoring period can be set to 0.01 second to 1 second. The period cannot be too short, it is easy to occupy too many resources, and the cycle cannot Too long to prevent the outside world from stealing data quickly.

3) Compare the monitored capacitance value with the standard value. When the set threshold value is exceeded, proceed to step 4). Otherwise, proceed to step 2); the set threshold value is related to the accuracy of the detection device, which may be 0.1pF- 1pF;

4) Wipe important data in the electronic device. It can be erased in an empty manner, or it can be formatted or destructively processed in a specific way (equivalent to altering the data content) so that the thief cannot know the actual data content.

Among them, the signal line is usually multiple (because one electronic device is connected by multiple electronic devices), when the power is detected, the standard value of the stray capacitance of each signal line is recorded one by one; when the power is on, the sequence is monitored or The stray capacitance of each signal line is randomly monitored and compared with its corresponding standard value.

There are two ways to monitor the stray capacitance of a signal line:

The first method uses the direct monitoring method. The direct monitoring method is to charge and discharge the stray capacitance of the signal line, monitor the voltage of the stray capacitance and the charge and discharge time, and then calculate the capacitance value of the stray capacitance by the charge and discharge formula of the capacitor. . This method can be implemented by using a capacitance detecting chip, such as the embodiment shown in FIG. 6, which is a capacitance detecting chip of the GT811 type.

The first method uses an indirect monitoring method. By monitoring the oscillation frequency of the RC oscillation circuit or the LC oscillation circuit connected to the stray capacitance, the capacitance value of the stray capacitance is calculated by the formula of the oscillation frequency. A selection circuit is provided between each signal line and the RC oscillation circuit or the LC oscillation circuit, and the connection of each signal line to the RC oscillation circuit or the LC oscillation circuit is turned on one by one by the selection circuit. For example, in the embodiment of Figures 3-5, an RC oscillator circuit and an 8-channel multiplexer chip are implemented.

As shown in FIG. 2, the data information protection circuit of the electronic device of the present invention is an POS machine 10, and is provided with a processor 20 and a plurality of electronic devices 30 connected to the processor 20, including and detected. The capacitor 40 is electrically connected to the capacitor detecting module 50. The capacitor detecting module 50 is an RC oscillating circuit including an inverter (using a change in stray capacitance on the detected wire to change the charging and discharging time in the oscillating circuit, thereby changing the oscillating circuit. The output frequency is called a capacitance detecting module. The detecting end 51 of the capacitance detecting module 50 is connected to the detected wire 40, and the pulse detecting end 52 of the capacitance detecting module 50 is connected to the processor 20. The POS device 10 is first used. During electrical detection, the stray capacitance on the detected wire 40 and the capacitance detecting module 50 form a fixed pulse signal, which is transmitted to the processor 20, and the processor 20 records the frequency of the pulse signal as a standard frequency; during use, the processor 20 compares the received real-time frequency with the standard frequency, when the difference between the real-time frequency and the standard frequency (this difference may be positive or negative) exceeds the setting The value (this setting value depends on the value of the frequency change caused by the normal interference, which may be 1% of the standard frequency, or 0.1% of the standard frequency), the processor 20 determines that foreign matter contacts the detected wire 40, The stray capacitance on the detected wire 40 changes, the pulse signal formed by the combination with the capacitance detecting module 50 also changes, and the processor 20 outputs an alarm signal and/or a signal for protecting important data. The detected wire 40 is a connecting wire between the electronic device 30 and the processor 20 . In this embodiment, a more preferred solution is: an 8-channel analog multiplexer 60 is provided between the plurality of detected wires 40 and the capacitance detecting module 50, and eight input terminals 61 connected to the detected wires are provided. An output terminal 62 connected to the capacitance detecting module 50, and three control input terminals 63 connected to the processor 20, the 8-channel analog multiplexer 60 determines one of the input terminals based on the combined signals of the three control input terminals 63. Connected to the output. When powering up for the first time, the processor 20 inputs 8 combined signals one by one to the 8-channel analog multiplexer 60, and records the pulse frequency generated by the detected wire and the capacitance detecting module corresponding to each combined signal as the combination. The standard frequency corresponding to the signal; during use, the processor randomly or separately sends a combined signal, and compares the received real-time frequency with a standard frequency corresponding to the combined signal, when the real-time frequency corresponds to the standard frequency of the combined signal When the difference exceeds the set value, the processor determines that a foreign object contacts the detected wire corresponding to the combined signal, and the stray capacitance on the detected wire changes, and the pulse signal formed by the combination with the capacitance detecting module also occurs. Change, the processor outputs an alarm signal and/or a signal that protects important data.

The electronic devices include buttons, display screens, IC card readers and magnetic card readers. In other embodiments, the electronic device can also be an ATM machine or a cash register.

As shown in another embodiment of the present invention, the data information protection circuit of the electronic device of the present invention is an POS device, and the data information protection circuit includes a multi-channel selection module and a capacitance detection module:

The multi-channel selection module (ie, the multiplexer) is provided with a digital selection terminal, an external signal input terminal, and a signal output terminal. Specifically, the multi-channel selection module is a multi-channel selection chip, and the model of the chip is 74HC4051, and the design thereof is There are 3 digital selection terminals (S0 to S2), 8 external signal input terminals (A0 to A7) and 1 signal output terminal A. The A0 to A7 pins are connected to important signal lines, such as button scan lines and IC cards. Data lines, etc.; S0 to S2 are respectively connected to three signal lines LED0, LED1 and LED2, The central processor can output the signal output signal A of the A0 to A7 of the 74HC4051 by controlling the three signal lines of LED0, LED1 and LED2.

The capacitance detecting module includes a first inverter U418A of type 74HC14, a second inverter U418B, and a third inverter U418C. The input terminal 1 of the first inverter U418A passes through the first capacitor C35 and the multiplexer module. The output terminal A is connected, the output terminal 2 of the first inverter U418A is connected to the input terminal 3 of the second inverter U418B, and the output terminal 4 of the second inverter U418B is connected to the input terminal 5 of the third inverter U418C. A first resistor R1 is connected between the input terminal 1 and the output terminal 2 of the first inverter U418A, and the input terminal 1 of the first inverter U418A and the output terminal 4 of the second inverter U418B are sequentially connected in series. The second resistor R2 is connected to the second capacitor C37, and the connection point 8 of the two is connected to the output terminal 6 of the third inverter U418C through the third resistor R3. The input terminal 5 and the output terminal of the third inverter U418C. 6 is connected to its output terminal Key-LED through a fourth resistor R4 and a fifth resistor R5, respectively.

The power input terminal VCC33 of the first inverter U418A is grounded through the parallel connected third capacitor C207 and the fourth capacitor C135, so that the interference of the alternating current signal to the circuit can be filtered out.

During operation, the central processor outputs the data on one of the A0-A7 pins of the multi-channel selection chip 74HC4051 to the signal output terminal A by controlling the three signal lines of LED0, LED1, and LED2. After strobing a certain path in A0-A7, the stray capacitance of any one of A0-A7 and the resistors R1, R2, and R3 form a loop of RC charge and discharge. When the POS machine is not turned on, there is no charge on the first capacitor C35 and the stray capacitance; when the POS machine is turned on, the capacitance detection module starts to work, and the input terminal 1 of the first inverter U418A is low level, and the output terminal 2 When it is high level, after the second inverter U418B and the third inverter U418C are reversed twice, the output terminal 6 of the third inverter U418C is also high level, and the first inverter U418A The third inverter U418C charges the stray capacitance of any one of the first capacitors C35 and A0-A7 through the first resistor R1 and the second resistor R2. The voltage waveform at the input terminal 1 of the first inverter U418A is as shown by Vc in FIG. 2, and when t0, the voltage at the input terminal 1 of the first inverter U418A reaches VT+, and the first inverter U418A considers that the input is high. In the flat state, the output terminal 2 becomes a low level, and the output terminal 6 of the third inverter U418C also becomes a low level. The waveforms of the output terminal 2 of the first inverter U418A and the output terminal 6 of the third inverter U418C are as shown by Vo in FIG. At this time, the stray capacitance of any one of the first capacitor C35 and A0-A7 is discharged through the first resistor R1 and the second resistor R2, and the discharge is located in the time period t0-t1, when the voltage of the first inverter U418A falls to In VT-, the first inverter U418A considers that the input is low, the output terminal 2 becomes high level, and the output terminal 6 of the third inverter U418C also becomes high level, and the first inversion is performed at this time. The U418A and the third inverter U418C further charge the stray capacitance of any one of the first capacitors C35 and A0-A7 through the first resistor R1 and the second resistor R2, and the waveform is as shown in the t1-t2 period of FIG. Shown.

The capacitance detecting module continuously switches between the charging and discharging states under the action of the multi-way selection chip 74HC14, and the voltage on the stray capacitance of any one of the first capacitor C35 and A0-A7 forms a periodic signal, and at the same time An inverter U418A, a second inverter U418B, and a third inverter U418C each have a waveform conversion function such that the output terminal 4 of the second inverter U418B outputs a rectangular wave of a certain frequency. The frequency of the rectangular wave is 1/(T1+T2), which is related to the stray capacitance of any one of the first capacitors C35 and A0-A7 and the first resistor R1 and the second resistor R2. When any one of the A0-A7 is mixed When the bulk capacitance changes, the frequency also changes. At this time, the central processor determines whether the stray capacitance of any one of the A0-A7 changes by detecting whether the frequency changes.

When someone tries to detect important data in a POS machine, there are generally two ways to directly detect these signal lines or find ways to disable the capacitance detection circuit. If the direct detection method is used, the illegal personnel will use the probe and the probe to detect the signal on the data line. Although the capacitance distributed on the probe and the probe is relatively small, the current probe and probe generally have a capacitance of at least 5 pF. However, the capacitance detecting module in the embodiment of the present invention uses a high-precision, small-temperature-sensitive capacitor, and the optimization of the software algorithm can detect the change of the 1pF capacitor, which is much smaller than the probe and the probe with 5pF. Capacitance, therefore, makes it very difficult to detect the signal on the data line with the probe. When the probe and probe detect the signal on the data line, the stray capacitance of any one of the A0-A7 will change. It also changes, the central processor immediately erases the protected data, effectively protects the data from being stolen, and important data lines can also walk in the inner layer of the PCB to reduce the possibility of detection; In the module failure method, the illegal person first measures the frequency of the Key-LED signal at the output of the capacitance detection module, and then goes off the capacitance detection module in the shutdown condition, and so on. After powering on, input the signal of the same frequency as the Key-LED of the output of the capacitance detecting module to the central processing unit, but this can only be done with the same frequency as that of a certain signal line in A0-A7, and the central processing unit selects by digital The end continuously loops to detect the frequency of any one of the A0-A7, compared with the eight frequencies originally calculated by the central processing unit, and the signal injected into the central processing unit needs to constantly change the frequency to maintain the same frequency as the eight frequencies. It's hard to do, so it can also effectively protect data from being stolen. When the frequencies are inconsistent (ie, not identical), it is determined that a foreign object has contacted the detected wire, and the processor initiates an alarm signal or performs a related protection action, such as starting a self-destruction program and destroying important information data. The circuit of this embodiment can detect a change in the pulse frequency caused by the stray capacitance of the detected conductor being less than 1 PF, and generally the foreign matter (usually a conductor) contacting the detected conductor causes a change of 5PF, and therefore, basically, is detected. Any condition in which the wire is spit is detected. Among them, the eight input terminals of the 8-channel analog multiplexer can be used up. If there are not many wires to be detected, the excess input can also be blanked; 8 inputs can detect 8 detected wires, basically enough Protection of an electronic device.

In other embodiments, only two inverters may be used. The third inverter U418C in the above embodiment is for improving the load capacity; other types of inverters can also be used; the parameters of the resistors and capacitors can be adjusted according to actual needs. In other embodiments, if there are too many detected wires, it can be added to two multiplexers; if the capacitance detecting module is not enough, it can be increased to two.

In the embodiment shown in FIG. 6, the data information protection circuit of the electronic device of the present invention adopts a direct monitoring mode, and uses a GT811 type chip. Among them, SENS1-SENS7 are eight detection inputs connected to eight signal lines; the right side is a control terminal and an output terminal, and is connected to a processor (CPU) for receiving control signals and outputting the monitored capacitance values. Among them, R0-R7 is a current limiting resistor at the time of charge and discharge.

Direct measurement is performed by charging and discharging a capacitor, detecting the voltage of the capacitor, and the time of charge and discharge, and calculating the capacitance value by using the formula of charge and discharge of the capacitor.

For direct measurement, the formula used is as follows:

Let V0 be the initial voltage value on the capacitor; V1 is the voltage value that the capacitor can finally charge or put, and Vt is the voltage value on the capacitor at time t. Then, Vt="V0"+(V1-V0)* [1-exp(-t/RC)]. According to the formula, it is only necessary to detect the voltage value and the time of charge and discharge to calculate the capacitance value.

The capacitance is detected by the capacitive touch screen IC, and the measured capacitance value is compared with the capacitance value stored by the CPU. When the difference exceeds the threshold, the CPU erases important data.

In summary, the protection method of the present invention uses real-time monitoring of the signal line to acquire the change of the stray capacitance value on the signal line in real time, and when the change value exceeds the set threshold value, it is determined that the external conductor foreign object pair The signal line is detected, thereby erasing important data in the electronic device, and monitoring the stray capacitance to monitor the contact of foreign objects with the signal line to ensure data security in the electronic device. The method has the characteristics of simple implementation, safe and reliable, low cost, and can be applied to data security protection of various electronic devices in the field of informationization, such as electronic devices for electronic transactions and storage devices for important data.

The above technical description of the present invention is further described by way of example only, and is not to be understood by the reader, but the embodiments of the present invention are not limited thereto, and any technology extending or re-creating according to the present invention is subject to the present invention. protection of. The scope of the invention is defined by the claims.

Claims

A data information protection method for an electronic device, characterized in that the method comprises the following steps:

1) Perform power-on detection on the electronic equipment that has been completed for production and installation, and detect the stray capacitance of the signal line, and record it as the standard value of the signal line;

2) Monitor the stray capacitance of the signal line when powering up;

3) comparing the monitored capacitance value with the standard value, when the set threshold value is exceeded, proceed to step 4), otherwise, proceed to step 2);

4) Wipe important data in the electronic device.
The data information protection method for an electronic device according to claim 1, wherein the signal lines are plural, and when the power is detected, the standard values of the stray capacitances of the signal lines are recorded one by one; The stray capacitance of each signal line is sequentially monitored or randomly monitored and compared with its corresponding standard value.
The data information protection method for an electronic device according to claim 2, wherein the stray capacitance of the signal line adopts a direct monitoring method, and the direct monitoring method is to charge and discharge the stray capacitance of the signal line, and monitor The voltage of the stray capacitance and the charge and discharge time are used to calculate the capacitance of the stray capacitance using the charge and discharge formula of the capacitor.
The data information protection method for an electronic device according to claim 2, wherein the stray capacitance of the signal line adopts an indirect monitoring method, and the indirect monitoring method is to monitor an RC oscillating circuit or LC connected to a stray capacitance. The oscillation frequency of the oscillation circuit calculates the capacitance value of the stray capacitance by the formula of the oscillation frequency.
The data information protection method for an electronic device according to claim 4, wherein a selection circuit is disposed between each of the signal lines and the RC oscillation circuit or the LC oscillation circuit, and each of the signal lines is turned on one by one by the selection circuit. Connection to RC oscillator circuit or LC oscillator circuit.
A data information protection circuit for an electronic device, wherein the electronic device is provided with a processor and an electronic device connected to the processor through a signal line, and is characterized by comprising a capacitance detecting module electrically connected to the signal line, the capacitance detecting module The detecting end is connected with the signal line, and the pulse detecting end of the capacitance detecting module is connected with the processor; when the electronic device is first powered on, the stray capacitance on the signal line and the pulse signal formed by the capacitance detecting module are transmitted to a processor, the processor records the frequency of the pulse signal as a standard frequency; during use, the processor compares the received real-time frequency with a standard frequency, and when the difference between the real-time frequency and the standard frequency exceeds a set value, the processor It is determined that there is a foreign matter contacting the signal line, the stray capacitance on the signal line changes, the pulse signal formed by the combination with the capacitance detecting module also changes, and the processor erases important data in the electronic device; the signal line is electronic A connecting wire between the device and the processor.
A data information protection circuit for an electronic device according to claim 6, wherein said capacitance detecting module is an RC oscillating circuit including an inverter; said signal lines are a plurality of; said plurality of A multiplexer is provided between the signal line and the capacitance detecting module.
A data information protection circuit for an electronic device according to claim 7, wherein said multiplexer is an 8-channel analog multiplexer, and has eight input terminals connected to the signal line and a pair The output of the capacitance detecting module is connected, and three control inputs connected to the processor. The 8-channel analog multiplexer determines that one of the input terminals is connected to the output terminal according to the combined signals of the three control inputs; The processor inputs 8 combined signals one by one to the 8-channel analog multiplexer, and records the signal line corresponding to each combined signal and the pulse frequency generated by the capacitance detecting module as the standard frequency corresponding to the combined signal; During use, the processor randomly or separately sends a combined signal, and compares the received real-time frequency with a standard frequency corresponding to the combined signal, when the difference between the real-time frequency and the standard frequency corresponding to the combined signal exceeds the set value. When the processor determines that a foreign object contacts the signal line corresponding to the combined signal, the stray capacitance on the signal line changes, The pulse signal formed by the combination of the capacitance detecting module also changes, the processor outputs an alarm signal and/or a signal for protecting important data; the electronic device is a POS machine, an ATM machine or a cash register; and the electronic device includes a button , display, IC card reader and magnetic card reader.
A data information protection circuit for an electronic device, wherein the electronic device is provided with a processor and an electronic device connected to the processor through a signal line, and is characterized by comprising a capacitance detecting module electrically connected to the signal line, the capacitance detecting module The detecting end is connected with the signal line, the control end and the signal output end of the capacitance detecting module are connected with the processor; the capacitance detecting module is a capacitance detecting chip; when the electronic device is first powered on, the capacitance detecting module detects the signal line The stray capacitance is transmitted to the processor, and the processor records the capacitance value as a standard capacitance value; during use, the processor receives the capacitance value detected by the capacitance detecting module in real time and compares it with the standard capacitance value when the real-time capacitor When the difference between the value and the standard capacitance value exceeds the set threshold, the processor determines that there is a foreign matter contacting the signal line, and the processor erases the important data in the electronic device.
A data information protection circuit for an electronic device, characterized in that the electronic device is a POS machine, and the data information protection circuit comprises:

The multiplex selection module is a multiplex selection chip, and the multiplex selection chip is 74HC4051, which has 8 external signal input terminals (A0 to A7) and 3 digital selection terminals (S0). To S2) and one signal output (A);

a capacitance detecting module, the capacitance detecting module comprising a first inverter (U418A), a second inverter (U418B), and a third inverter (U418C), an input end of the first inverter (U418A) (1) Connected to the output (A) of the multiplexer (90) via the first capacitor (C35), the output (2) of the first inverter (U418A) and the input of the second inverter (U418B) (3) Connection, the output terminal (4) of the second inverter (U418B) is connected to the input terminal (5) of the third inverter (U418C), and the input terminal (1) of the first inverter (U418A) A first resistor (R1) is connected between the output terminal (2) and the output terminal (4) of the first inverter (U418A) and the output terminal (4) of the second inverter (U418B). The second resistor (R2) connected in series and the second capacitor (C37) are connected, and the connection point (8) of the two is connected to the output terminal (6) of the third inverter (U418C) through the third resistor (R3). The input terminal (5) and the output terminal (6) of the third inverter (U418C) are connected to the output terminal (Key-LED) through the fourth resistor (R4) and the fifth resistor (R5), respectively. A first inverter (U418A) of the power supply input (the VCC 33) connected in parallel through a third capacitance (C207) and a fourth capacitance (C135) to ground.